Energy saving and power reduction have been and will continue to be an area of prime interest in the wireless communication community. Almost every mobile device manufacturer and provider is required to implement and incorporate into their mobile terminal products power-saving techniques as required under the wireless communication standards, such as the mandatory features of handset discontinuous transmission (DTX) and reception (DRX) that can help improve the battery life in mobile products. Most mobile network operators or carriers are also faced with strong requirements to reduce their greenhouse emissions and energy consumption as they keep building out and maintaining the network infrastructure in order to provide better wireless communication services to customers. In recent years, the deployment of network equipment on a massive scale has led to a steady increase in pollution and energy consumption worldwide. Particularly in emerging markets where basic infrastructure elements, such as electricity grids and connections, are often underdeveloped, there is even higher energy consumption due to the network operator's use of conventional equipments such as diesel generators in building cell towers and base station sites. As a result, many authorities ranging from local governments to international organizations have formulated and are enforcing environmental requirements that mobile network operators need to comply with. Energy Saving (ES) mechanisms are becoming an integral part of the new generation radio access networks such as LTE, and consequently, of most wireless communication systems. A good ES solution needs to ensure no service degradation or inefficiencies in the network. This means, backward compatibility should be fully considered in designing an ES scheme, especially in networks that serve a number of legacy user equipments (UEs).
A large part of the network energy consumption is attributed by the power usage in base stations of a wireless communication network. In addition to power consumed for active cooling, different base station components, whether in a receiver or transmitter, need power to perform baseband processing, signal processing and many other computing tasks. In particular, the RF components in a base station, mainly the power amplifier (PA) in a transmitter, consume large amounts of power. Part of the power transmitted from an antenna can be lost in the PA. Sometimes the PA efficiency (defined as a ratio between the PA output power and input power) can be less than 50%. Such power loss can only be avoided by temporarily turning off the PA. Therefore, determining how to reduce power loss and consumption in a PA can be crucial to the overall energy efficiency in a base station, which ultimately can significantly contribute to the network energy savings in the entire wireless communication system.